Creep behavior of cylindrical specimens under natural environmental andcontrolled conditions.
Nagaoka University of Technology
Nagaoka University of Technology
Regular Member

Ifeajika Victor
Shimomura Takumi

1. Introduction.
Concrete creep and the associated long-term deflections areboth influenced by environmental conditions, mixing
proportions, material properties and applied stress.
Throughout it service life, concrete structures will be exposed toloading in conjunction with variable environmental conditions.
However, the long term behavior of concrete under suchvariable environmental condition merits further investigation.
Actual Structures are exposed to cyclic outdoor environmental
conditions but in the prediction of creep effect on the long term
deflection of concrete structures, data for creep strains are
obtained from experiment conducted in controlled conditions.
Further-more, if creep characteristics of concrete are determinedby tests, the environment conditions of such texts should beapproximate to those of the actual structure. The effect ofoutdoor exposure mitigates in the accurate prediction of timedependent deformations.

2. Experimental Study.
2.1. Test specimens.
Hollow cylinders were selected for this study with twodifferent sealing conditions. One types of specimen wereunsealed and exposed to radial and axial drying with a volume
to surface ratio of 25mm, while the second specimen wasradially sealed and exposed to drying in its axially direction,with a volume to surface ratio of 100mm.
The specimens were exposed to natural environmental
condition and controlled room condition of 20 degrees Celsius
and 50 % relative humidity.
2.1.1. Test set up for Creep behaviour
The creep behaviour of plain concrete were carried out toinvestigate the creep behaviour under outdoor conditions. The
type of cement used was ordinary Portland cement. The
compressive strength and Young’s modulus in Table 2 wereobtained by compressive test using ф100*200 mm cylinder
specimens after 7 days and 28 days after moist curingrespectively.
Six Hollow cylinders of dimensions 200 mm in height and 100mm outer diameter and 30 mm inner diameter were cast with(high volume/surface area V/S = 100 mm) radially sealedspecimen and (with lower volume /surface area V/S = 25 mm)
for Unsealed specimen. The lateral surface of the radiallysurface was treated with epoxy to prevent moisture loss for its
lateral surface.

A sustained compressive load; 20 percent of concrete
compressive strength, was applied to the specimens by handfastening the prestressing steel bars with nuts. The applied stress
was calculated by checking the average strain value obtained
from two 2 mm electric strain gauges attached to the lateralsurfaces of the specimens as shown in Fig. The applied stress
was approximately 20% of the compressive strength of concreteat 7 days and 28 days respectively.
After the stress were applied, the specimens were exposed tonatural environmental and control room conditions. The
longitudinal strains were measured using electric strain gauges
attached on lateral surface of the specimens.
2.1.2. Environmental conditions.
The hollow cylindrical specimens were loaded at 7 days and
28 days after curing respectively and exposed to naturalenvironmental conditions and control room conditions on 6th
August and 26th of August 2019 respectively, at the campus of
Nagaoka University of Technology, the average weather
distribution of the test location is situated at the Nagaoka
University of Technology campus.
3. Results & discussion.
Figure 2 shows the variable weather data that were recorded
regularly during the tests period.
3.1. Creep Strain.
Figure 3 shows creep strain curve for the specimens undernatural environment conditions and control room conditions.
The development of creep strain in unsealed specimen increases

considerably during the first ten days and converges beyond
twenty days. High early creep strain was noticed in the creep
strain curve for environmental exposure and control room
condition for specimens loaded at 7 and 28 days respectively,
however creep stain curves for unsealed specimen was highest
in control condition specimen over time.
The creep strains of curves of radially sealed specimens
increase considerably during the first five days and exhibit linear
tendencies. During low temperature and high relative humidity
periods, swelling is noticeable in specimen loaded at twentyeight days. The creep strain curve for specimen in loaded at 7days in outdoor environment is highest.
Age at loading effect on creep behaviour was investigated. In
specimens loaded at 7 days and exposed to Outdoor
environment, High drying creep strains were measured with arelative high basic creep.
In specimens loaded at 28 days and placed in Outdoor field,
High drying creep strains were also measured with a lower basic
creep due noticeable swelling at the first ten days after loading.
Specimens loaded at 28 days and placed in control room
environment exhibited low drying shrinkage compared tospecimens in Outdoor environment, However, it was also notedthat shrinkage strains were higher than creep strains. Hence incontrol room environment, the moisture loss in unloadedspecimen is higher than loaded specimens

5. Conclusions.
An experimental investigation on the effect of age at loading andoutdoor natural environment on concrete creep was carried out.
1) The effects of age at loading saw a considerable increasein basic creep strains for specimens exposed to outdoor
environment conditions.
2) Rainfall, low temperature and high relative humidity
inhibited the progression of drying shrinkage leading toswelling.
3) The magnitude of shrinkage strains was observed to behigher for specimens exposed to drying in controlconditions.
4) Rainfall inhibited the progression the progression of total
creep during early ages.
5) Creep coefficient was observed to be higher for specimens
exposed to outdoor environmental conditions.
6) Rainfall is noticed to be an influential parameter for timedependent strains of specimens exposed to naturalenvironmental conditions.
References.
[1] Pengfi li and Shiqin He, 2018, Effects of variable Humidity
on the Creep behavior of concrete and the Long term
Deflection of RC Beams, Proceedings of Advances in Civil
Engineering．
[2] Shingo Asamoto, Ayumu Ohtsuka et al; 2011, Study on
effects of solar radiation and rain on shrinkage, shrinkage
cracking and creep of concrete, Proceedings of theCement and Concrete Research Journal, Vol. 41, No. 2, pp.
590-601．
[3] A.M. Neville, W. H. Dilger and J. J. Brooks, 1982, TimeCreep of plain and structural concrete, Construction Press,London.
[4] RILEM TC 107 CSP Recommendation, ‘measurement oftime-dependent strains of concrete, Materials andStructures, Vol. #1, October 1998, pp 507-512.